I replied by noting that I wouldn’t call their belief ridiculous since such a statement would be “rude and condescending”. It would be more appropriate to call the belief in question “irrational” or “unjustified”, for rationality and justification are formal epistemological descriptors and do not convey the inflammatory hostility and derision that is implied by the descriptor “ridiculous”.

But there is another problem. One can readily envision an instance of astrological belief (and presumably crystal belief as well) that is not obviously irrational or ridiculous. I explained as follows:

“Imagine a young man named Billy who has been taught astrology since he was young. He has seen some striking examples of astrological predictions being confirmed and he has not been presented with any strong evidence against astrology. Are his beliefs ‘ridiculous’? I don’t think they are. Given Billy’s data set, they are reasonable.”

(I discuss an illustration like this — one that involves a flat earther — at much greater length in my book You’re not as Crazy as I Think.)

After I made this point, David Evans offered the following reply to my Billy case:

“Billy is not behaving ridiculously in believing as he does. But that’s because he lacks the relevant knowledge through no fault of his own. I see nothing wrong in saying that for anyone who possesses the relevant knowledge (about astronomical forces and distances, among other things) to believe in astrology would be ridiculous.”

Alas, I still don’t understand the felt need to call the beliefs of others ridiculous. As I already pointed out above, there are non-inflammatory terms ready at hand for substandard beliefs: irrational and unjustified. Calling a belief “ridiculous” substitutes the technical precision of those terms with inflammatory condescension and that does nothing but poison discourse. When you call the beliefs of other people ridiculous you introduce a sense of contempt. And contempt for dissenting opinions is, in my view, one of the greatest enemies of the open society.

There is one condition under which it would be relevant to introduce an inflammatory tone to the discourse, and that is when one believes the other’s belief is deserving of moral censure. Let’s say, for example, that you meet a neo-Nazi who insists that Jews are not fully human. It would be appropriate to call such a belief morally offensive, but it would also be appropriate to denounce it with a more inflammatory term like “appalling” or “evil”. This is at least in part because proper moral thinking includes attraction and revulsion (though, contrary to the emotivists, it cannot be reduced to it).

However, when the issue is a matter of perceived irrationality rather than immorality, I do not see any benefit in denouncing a person’s beliefs as ridiculous. As I said, this does nothing more than foment contempt for others.